slang mostly, I mod a strictly 18+ space and recently someone used the word "skeet", and would you believe it, they were a minor

"skibidi" "rizz" "sus"

Vertical filming, putting music into videos when you could just use silence

Crypto bros who follow ultra distorted stoicism (the only good philosophy is the ones made when slavery was normalised) that believe everyone else is unaware of what very basic knowledge they world they just learned that day.

"im 9 btw"

Unfaltering loyalty to the Chinese Communist Party

Probably just internet slang and the skull emoji. That and poor grammar are (possible) indicators.

Quick to call other people kids as an insult.

Writing in short form where a lengthier reply would work better and when confronted with such a reply some form of "not reading all that" or other thought terminating clichés.

I've found that as arbitrary as it is - the ability to read a lot of information works pretty well as a mark of mental maturity. Also links to Twitter or Tiktok as discussion points. No one over the age of 19 browses TikTok lol.

When they start calling people "jr" or implying anyone who disagrees with them is too young to understand.

This one has been easy for me lately: They spell 'lose' as 'loose'.

They’re the ones who are not obsessing over children’s toys or saying “adulting is difficult!”.

skibidi toilet

"Arguing" by listing a long list of fallacies that they don't really even understand.

Fallacy fallacy!

When someone explains something everyone knows or is obvious as if they just thought of it for the first time in human history.

Biologically a kid or adults too?